Romeo Ciobanu, Cristina Schreiner, Marinel Temneanu
UPON THE DIFFERENCE BETWEEN THE EVOLUTION VERSUS FREQUENCY OF PD AND BREAKDOWN PROCESSES, RELATED TO PAPER FOR DC CABLES INSULATION

Significant differences between the evolution versus frequency of the PD and breakdown processes were emphasized, suggesting that the breakdown analysis, if used as unique method in quality assessment of insulating materials, proves to have limits in accuracy and may lead to errors in results interpretation.

Patrick Boets, Leo Van Biesen
METALLIC 2-WIRE PARAMETRIC LINE MODELS - A SURVEY

A survey of frequency domain models to describe cables of the access network of operators is presented. The cable characteristics of some commercial cables are measured and the parameters of the used models identified. From this, the properties and application areas of physical models as well as rational functions are discussed. It will be demonstrated and explained why some frequently used cable models show an unrealistic impulse behavior.

Tomasz Tarasiuk, Janusz Mindykowski
IN THE SEARCH OF THE EFFECTIVE ASSESSMENT METHOD OF ELECTRIC POWER QUALITY ON SHIPS

This paper concerns the problem of proper evaluation of power quality in naval networks. Two aspects of the problem have been addressed. Firstly, the appropriate choice of power quality parameters for the aim has been discussed. Secondly, the methods of their estimation especially concerning aggregating of measurement intervals have been discussed. These considerations will be based on the basis of the original authors’ research carried out in ship electrical power systems and relevant examples from this work will be given. Presented paper is a continuation and complementary part of the earlier works carried out by the same authors.

Pietro Vincenzo Barbaro, Antonio Cataliotti, Valentina Cosentino, Salvatore Nuccio
A NEW TECHNIQUE TO DETECT HARMONIC SOURCES IN POLLUTED POWER SYSTEMS

This paper presents a comparative analysis among different nonactive power quantities proposed in literature in nonsinusoidal conditions; with respect to this, a new single-point approach is proposed, for the detection of the dominant harmonic sources in polluted power systems. It is based on the observation that in the same distorted working condition the analyzed power quantities present a different behavior. In order to verify the theoretical assumptions, some simulations tests were carried out on a standard IEEE test system, proposed as a benchmark for harmonic propagation studies. Simulation results show how the approach based on a comparison of different definitions of nonactive powers can give some useful information for the detection of dominant harmonic sources.

Dušan Agrež
FAST MEASUREMENT OF POWER SYSTEM FREQUENCY IN THE FREQUENCY DOMAIN

In paper, an algorithm for fast measurement and estimation of power system frequency is presented. The frequency is calculated by an interpolation of the amplitude coefficients of the discrete Fourier transform (DFT). An analysis is made to study the influence of the leakage effect when the rectangular window and the Hanning window are used. Interpolations with longer time of measurement and with larger number of points decrease the systematic errors. The proposed method achieves accuracy in measuring the frequency under a hundredth of Hertz.